FIG. 9 is a block diagram of conventional active noise control device 501. Active noise control device 501 reduces a noise generated due to a rotation of a vehicle engine in a vehicle compartment by generating an acoustic wave having the same amplitude as the noise and a phase opposite to the noise, and causing the acoustic wave to interfere with the noise.
A control signal for generating the acoustic wave interfering with the noise is generated by multiplying a sine-wave signal and a cosine-wave signal which have the same frequency as the noise by adaptive filter coefficients, and summing the sine-wave signal and the cosine-wave signal.
An adaptive filter is updated by an LMS algorithm based on a reference signal of a sine-wave signal and a simulation signal which is generated by convoluting a transfer characteristic between a loudspeaker and a microphone with a signal from the microphone located at a control point.
PTL 1 and PTL 2 are prior art information relating to active noise control device 501.